Apparatus and method for mixing multi-part reaction materials under vacuum

ABSTRACT

An apparatus for mixing multi-part reaction materials under a vacuum comprises a container including a mixing chamber sized to contain a reaction material. An agitator for mixing the reaction material to form a mix includes both rigid blades and flexible paddles. The rigid blades are substantially non-deflected during mixing and cut the mix, and the flexible paddles are deflected and knead the mix. The combined action of the rigid blades and the flexible paddles under vacuum throughly mixes reaction materials and removes entrapped gases from the mix. The mix can be dispensed directly from the mixing chamber. The apparatus can be used to mix viscous materials such as bone cement.

BACKGROUND

The present invention relates to an apparatus and method for mixingmulti-part materials under vacuum and for dispensing the mix from theapparatus.

Multi-part reaction materials are commonly mixed under vacuum toeliminate entrapped air and gaseous reaction byproducts from the mix.The mixing vessel can be evacuated after mixing, but before use, orduring mixing. Certain materials have relatively shorter set times andhigher viscosity. It is more difficult to remove gases from thesematerials for several reasons. First, bubbles formed during mixing mustmigrate through the viscous mix to reach a surface exposed to vacuum.Second, the vacuum level that can be used during mixing is limited bythe boiling points of the parts, as in bone cement; the differentialpressure attainable at a given altitude; and the capabilities of theapparatus that creates the vacuum.

A known method for mixing bone cement to increase the rate of entrappedgas elimination comprises pre-evacuating the space surrounding one partof the cement prior to mixing, and then introducing the other part intothe evacuated space. This method is less than completely satisfactory,however, because the turbulence caused by the second part filling theevacuated space can cause bubbles and voids to form in the mix.

It is also known to force a first part to replace the interstitial airin a second part. The air present in second material is displaced; butthe method does not quickly and thoroughly mix the two materials, removethe gaseous reaction byproducts, or compensate for temperature.

It is important in the mixing of certain multi-part materials, that thematerials be quickly combined and that the mix, de-air and de-gas stepsbe performed quickly, so as to protect the mix from outsidecontamination. Avoiding contamination is especially important in themixing of bone cement under sterile surgical conditions. Generally, bonecements have a mix schedule, from the addition of a liquid monomer to apowder component, of one minute for mixing followed by one minute of potlife, before the mix needs to be injected. Accordingly, the efficiencyof the mixing step is very important.

Some known methods of mixing bone cements comprise mixing materialswithin a container from which the mix is subsequently extruded, andapplying a vacuum to the container during the mix, or both during andafter the mix. Known methods agitate the bone cement mix to enhancemixing within the time constraints of the mixing process. Flat plateagitators having various hole patterns have been used to accomplish themix. The mixed material can be extruded from the mixing chamber throughthe plate. Mixing only occurs when the agitator is moved in and out ofthe mixing chamber. Rotary motion repositions the holes for axialplunging, but provides only minimal mixing.

Another important consideration in regard to multi-part reactionmaterials is that the parts be readily accessible and easily handeablebefore and during the mixing procedure.

Bone cement liquid monomer is an example of a component of a multi-partreaction material that is difficult to handle. The monomer is usuallydelivered by the bone cement manufacturer in a glass vial, which isbroken to add the monomer to the powder component. The monomer may notalways be stored within the container in which the mixing is performed,and may be supplied separately from the device. This can make the mixingprocedure more difficult to perform.

During the mixing of multi-part reaction materials under vacuum, gasescan be evolved. These gases can be toxic to humans, and so it isimportant to prevent these gases from escaping into the environment.

Accordingly, there is a need for an apparatus for mixing and dispensingmulti-part reaction materials that (i) can rapidly combine the materialsto meet mix schedules, (ii) does not cause cavitation in the mix,reducing the entrapment of air and out-gassing; (iii) efficientlyagitates the reaction materials throughout substantially the entiremixing chamber; (iv) can quickly establish and also maintain a vacuum inthe mixing chamber; (v) exposes a large amount of surface area of themix to vacuum during agitation, enabling trapped air and reaction gasesto escape from even viscous mixes.

SUMMARY

The present invention provides an apparatus and method for mixingmulti-part reactions materials under a vacuum that satisfies the aboveneeds. The apparatus comprises a first container including a walldefining an open first end, an open second end and a mixing chamber. Themixing chamber is sized to contain the reaction material during mixing.

The reaction material typically comprises a first part and a secondpart. For bone cement, the first part is a powder material and thesecond part is a liquid.

A closure can be provided at the second end of the first container toform an airtight seal.

An agitator includes an agitator rod partially disposed in the mixingchamber and extending outwardly of the first container through the firstend. The agitator rod preferably includes a bore through which thesecond part is introduced into the mixing chamber containing the firstpart.

The agitator comprises at least one rigid blade. The apparatuspreferably comprises at least four rigid blades. The rigid blades aresufficiently rigid so that they maintain their shape and are notdeflected during mixing of the reaction materials, such that the rigidblades can cut through the mix.

The agitator also comprises at least one flexible paddle fixedlyattached to the agitator rod. The apparatus preferably comprises atleast two flexible paddles. The flexible paddles are sufficientlyflexible to be deflected during mixing of reaction materials, such thatthe flexible paddles knead the mix.

The flexible paddles and the rigid blades preferably contact the wall ofthe mixing chamber to remove any reaction material adhered on the wallduring mixing.

A connector is typically attached to the first container at the secondend. The connector can include a first passage through which theagitator rod extends, and a second passage through which gases are drawnfrom the mixing chamber to produce a vacuum.

The second part of the reaction material is typically stored in a secondcontainer that can be removably attached to the connector.

The apparatus can comprise a vacuum pump attachable to the connector.The vacuum pump draws gases from the mixing chamber and can also pullthe second part into the mixing chamber. The first and second parts ofthe reaction material are mixed by the agitator.

The apparatus can also comprise a vacuum indicator to indicate thevacuum pressure in the mixing chamber.

The apparatus can comprise a plunger sized to be inserted into themixing chamber. The plunger moves axially in the mixing chamber duringdispensing of the mix from the first container.

The apparatus is particularly suitable for mixing multi-part reactionmaterials such as bone cement, including a liquid part and a solid part.The solid part is typically a powder that can be stored in the mixingchamber and the liquid part can be stored in the second container. Theapparatus protects the components from the environment prior to themixing. The two parts can be added to each other typically in accordancewith manufacturer specifications.

The present invention provides important advantages that enable rapid,uniform mixing of multi-part reaction materials under vacuum, including(i) rapid introduction of one part into another part, without causingcavitation in the mix and also reducing the entrapment of air; (ii)agitation of the mix throughout a substantial portion of the mixingchamber; (iii) agitation that exposes a large amount of surface area ofthe mix to vacuum, to enhance the escape of gases from the mix; (iv) anagitator that cuts the mix and scrapes the mixing chamber wall to plowone part into the other, without causing cavitation and out-gassing, andthat also kneads the mix; and (v) the ability to quickly establish avacuum in the mixing chamber and to maintain the vacuum.

DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood from the following description,appended claims and accompanying drawings, where:

FIG. 1 is a side elevational view of an apparatus for mixing multi-partmaterials under vacuum according to the present invention, prior to theintroduction of one part of a reaction material into a mixing chambercontaining another part of the reaction material;

FIG. 2 illustrates the apparatus of FIG. 1 after the two parts arecombined in the mixing chamber;

FIG. 3 is a partial cross-sectional view of the apparatus of FIG. 2;

FIG. 4 is an illustrational view showing the manner of attachment of therigid blades and flexible paddles to an agitator rod of the apparatus;

FIG. 5 is a cross-sectional view in the direction of line 5--5 of FIG. 3showing the configuration of the flexible paddles;

FIG. 6 is a cross-sectional view in the direction of line 6--6 of FIG. 3showing the configuration of the rigid blades; and

FIG. 7 is a cross-sectional view showing a breakable container forstoring one of the parts of the reaction material.

DESCRIPTION

With reference to the drawings, an apparatus 10 for mixing anddispensing multi-part reaction materials comprises a first container 12for containing a first component or first part of a reaction material.The apparatus can also comprise a second container 14 for containing asecond component or a second part of the reaction material and aconnector 16 attached to the first container 12. An agitator 18 isprovided to mix the reaction material. The apparatus 10 can comprise avacuum means such as a vacuum pump 20 to form a vacuum in the firstcontainer 12 during mixing.

The first container 12 comprises a wall 22 defining a mixing chamber 24,an open lower end 26 and an open upper end 28. The first container 12 ispreferably formed of a semi-rigid transparent or translucent material toenable the mixing process to be observed. The first container 12 istypically cylindrical shaped as shown. The mixing chamber 24 typicallyhas a relatively small volume which allows a vacuum to be readilyestablished and easily maintained. For example, the mixing chamber 24can have a diameter of from about 1 in. to about 3 in.

A plunger 30 is disposed in the mixing chamber 24. As described below,the plunger 30 is moved axially in the mixing chamber 24 duringdispensing of the mix from the mixing chamber 24.

A closure such as a removable cap 32 is attached to the wall 22 at thelower end 26. The cap 32 forms a gas-tight seal with the first container12 during formation of a vacuum in the mixing chamber 24.

Referring to FIG. 3, the connector 16 is removably attached to the upperend 28 of the first container 12 by mating threads 34 formed on theconnector 16 and the first container 12. A gasket 36 formed of aresilient material such as an elastomer is disposed to form a gas-tightseal between the first container 12 and the connector 16. The connector16 defines an axial first passage 38 through which an agitator rod 40 ofthe agitator 18 extends from outside of the connector 16 to inside ofthe mixing chamber 24. A connector nut 42 is removably attached to theconnector 16 by mating threads 44 formed on the connector 16 and theconnector nut 42. The connector nut 42 includes an opening 46therethrough for receiving the agitator rod 40. An O-ring 48 and aresilient gasket 50 form a gas-tight seal between the connector nut 42,the agitator rod 40 and the connector 16.

The agitator rod 40 preferably includes a longitudinal bore 52 extendingalong its length. A handle 53 is provided at an upper end of theagitator rod 40. A connector 54 such as a "Luer-Lok" connector isdisposed in the bore 52 proximate to the handle 53. A poppet 56 isdisposed at the lower end of the agitator rod 40.

The agitator 18 comprises at least one curved flexible paddle 58, and atleast one curved, rigid blade 60, attached to the agitator rod 40. Asshown in FIG. 4, the agitator 18 preferably comprises at least twoflexible paddles 58. The flexible paddles 58 are fitted on a threadedend portion 62 of the agitator rod 40 and extend radially outward towardthe wall 22. The agitator 18 preferably comprises at least four rigidblades 60 which also extend radially toward the wall 22. The rigidblades 60 can be approximately evenly angularly spaced from each otheras shown in FIG. 6. The rigid blades 60 include threads 64 for removableattachment to the threaded portion 62 of the agitator rod 40.

The flexible paddles 58 are sufficiently flexible so that they aredeflected by the mix during agitation, such that the flexible paddles 58knead the mix. The flexible paddles 58 are preferably sized to contactthe wall 22 of the mixing chamber 24 as shown in FIG. 5. Consequently,the flexible paddles 58 can effectively remove any of the mix adhered tothe wall 22 such that the reaction material is well mixed. The flexiblepaddles 58 can be comprised of a suitable metallic or non-metallicmaterial. For example, the material can be a plastic such aspolyethylene or nylon, or a resilient metal such as a spring steel. Theflexible paddles 58 typically have a thickness of from about 20 mil. toabout 40 mil. The thickness of the flexible paddles 58 can be varieddepending on the stiffness of the material from which they are formed.Generally, the stiffer the material, the thinner are the flexiblepaddles 58 to provide sufficient flexibility to knead the mix.

The rigid blades 60 are sufficiently rigid to maintain their shape andsubstantially not be deflected during agitation of the reactionmaterials, such that the rigid blades 60 can cut through the mix. Therigid blades 60 are preferably formed of a more rigid material than theflexible paddles 58. Accordingly, the thickness of the rigid blades 60does not need to be greater than the thickness of the flexible paddles58 to provide sufficient rigidity to substantially prevent deflectionduring agitation. The rigid blades 60 typically have a thickness of fromabout 20 mil. to about 40 mil. The rigid blades 60 can be formed of asuitable metallic or non-metallic material. The rigid blades 60 arepreferably sized to contact the wall 22 of the mixing chamber 24 asshown in FIG. 6. Consequently, the rigid blades 60 can cut through themix across the diameter of the mixing chamber 24.

Depending on the viscosity of the mix, the rigidity of the flexiblepaddles 58 and the rigid blades 60 can be varied such that the flexiblepaddles 58 are deflected and the rigid blades 60 are not deflected.Generally, as the viscosity of the mix increases, the rigidity of theboth of flexible paddles 58 and the rigid blades 60 is increased.

The number of flexible paddles 58 and rigid blades 60 can be varieddepending on the size of the first container 12. As the size of thefirst container 12 is increased, the number of flexible paddles 58 andrigid blades 60 is preferably increased to achieve effective agitationof the reaction materials. For example, the apparatus 10 can comprisetwo flexible paddles 58 and four rigid blades 60 as illustrated, orthree flexible paddles 58 and six rigid blades 60 (not shown). The sizeof the flexible paddles 58 and the rigid blades 60 can also be increasedas the size of the first container 12 is increased. The shape of theflexible paddles 58 and the rigid blades 60 can also be varied dependingon the physical characteristics of the reaction materials. The rigidblades 60 and the flexible paddles 58 are preferably fabricated asseparate components, so that different rigid blades 60 can be used incombination with flexible blades 58 of varying shape and flexibility,based on the physical characteristics of the reaction material to bemixed.

As shown in FIG. 3, the vacuum pump 20 can be removably attached to theconnector 16. The vacuum pump 20 comprises a tubular portion 66 which isinserted into a second passage 68 in the connector 16. The secondpassage 68 is in flow communication with the mixing chamber 24 via achannel 70 between the agitator rod 40 and the connector 16.

A gas filter 72 is typically disposed inside the tubular portion 66 toprevent the escape of potentially hazardous gases from the mixingchamber 24 into the surrounding environment. The filter 72 is typicallycomprised of a small pore size fabric and an absorbent material such asactivated charcoal for absorbing organic gas vapors. The filter mediumcan be selected depending on the materials that are mixed. There is onlya small amount of air moved by applying the vacuum with the filter 72positioned close to the mixing chamber 24 and with a high concentrationof vapors at this location, so that the amount of charcoal needed in thefilter 72 is small. The filter 72 prevents the harmful vapors that areevolved during the mixing of bone cement monomer from entering theenvironment.

A cap 74 is removably attached by mating threads 76 to the connector 16.

An O-ring 78 and a resilient gasket 80 form a gas-tight seal between theconnector 16 and the vacuum pump 20.

The vacuum pump 20 includes a grip 82 and a handle 84 pivotallyconnected to the grip 82 for grasping by a user. The handle 84 ispivoted to draw gases from the mixing chamber 24 via the channel 70, thesecond passage 68 and an exhaust outlet 86 of the vacuum pump 20, toproduce a desired vacuum level in the mixing chamber 24. A detachablevacuum indicator 88 shown in FIG. 2 can be provided to indicate thevacuum level in the mixing chamber 24.

The operation of the apparatus 10 is described in detail below withreference to the mixing of bone cement. The apparatus can be used to mixand dispense other multi-part reaction materials as well. The reactionmaterials can comprise, for example, two liquids, two pastes, or apowder and a liquid. The reaction material can be a cement as well asother types of materials such as adhesives. The reaction materials canhave different viscosities and set times. The apparatus 10 isparticularly advantageous for mixing viscous, short mix time reactionmaterials.

Bone cements comprise a liquid part and a powder part. The liquid part,typically a monomer such as methyl methacrylate, is conventionallysupplied in a glass vial 90 or the like as shown in FIG. 1. The glassvial 90 can be placed into the second container 14 to store the monomerprior to mixing with the powder part. The powder part can be polymethylmethacrylate. The vial 90 can be placed into the second container 14 atthe time of use, or alternately can be pre-packaged in the secondcontainer 14. The second container 14 is attached to the handle 53 ofthe agitator rod 40 at the connector 54. The agitator rod 40 can bemoved up and down, as well as rotated, relative to the mixing chamber24, while maintaining a vacuum in the mixing chamber 24. The agitatorrod 40 is held in an axial fixed position by contact with the O-ring 48and the gasket 50, and by contact between the flexible paddles 58 andthe rigid blades 60 against the wall 22 of the first container 12.

The powder part 92 of the bone cement can be placed into the mixingchamber 24 either at the time of use, or as a pre-packaged item, byremoving the cap 32 and the plunger 30 from the first container 12, andwith the second container 14 detached from the agitator 18, the powderpart 92 can be poured into the mixing chamber 24, passing through theopen structure of the rigid blades 60 and the flexible paddles 58, andnot entering the bore 52 of the agitator rod 40 due to the presence ofthe poppet valve 56. The plunger 30 is then placed back into the mixingchamber 24 at the lower end 26 followed by the attachment of the cap 32.The plunger 30 and the cap 32 each form an air-tight seal with the wall22 of the first container 12 when a vacuum is formed in the mixingchamber 24. The filter 72 prevents the powder part 92 from escaping whenthe plunger 30 is in the mixing chamber 24; however, gas can passthrough the filter 72 to enable the plunger 30 to be inserted into themixing chamber 24.

Upon commencement of mixing, the cap 32 is in direct contact with theplunger 30 and the second container 14 is attached to the agitator rod40. The cap 32 is placed on a solid surface such that the apparatus 10is in an upright position, and the second container 14 is positioned asshown in FIG. 1. A retainer 94 disposed at the upper end of the secondcontainer 14 is then pushed downward, pushing the vial 90 against abreaker 96 in the second container 14 as shown in FIG. 7, so as to breakthe vial 90. Breaking the vial 90 allows the liquid part contained inthe vial 90 to flow out through a filter screen 98, a connection portion100 which engages the connector 54, and into the bore 52 of the agitatorrod 40. Alternately, if there is a port valve (not shown) within theconnector 54, the liquid part does not fill the agitator rod 40 at thistime. A vent hole 102 is formed through the wall of the retainer 94 toallow air to enter the second container 14. This enables the liquid partto be easily pulled into the powder part 92. A one-way valve (not shown)can be provided in the vent hole 102 to allow air flow only in thedirection into the second container 14. The bottom end 104 of theretainer 94 can be tapered as shown to approximately match the shape ofthe portion of the vial 90 that it contacts to enhance breaking of thevial 90. O-rings 106 can be provided on the retainer 94 to preventvapors from escaping from the second container 14.

Following the breaking of the vial 90, the agitator rod 40 is pulledupward to above the powder part 92 in the mixing chamber 24. During theretraction of the agitator rod 40, some of the liquid in the bore 52 ofthe agitator rod 40 is pulled into the powder part 92. Once the flexibleblades 58 and the rigid blades 60 are positioned above the powder part92 in the mixing chamber 24, the handle 84 of the vacuum pump 20 can beslowly squeezed to gently pull the liquid down into the mixing chamber24 and sprinkle it through the poppet valve 56 onto the powder part 92.

Alternately, if a port valve is located at the connector 54, the monomermay be added only to the top of the powder part 92, with liquid appliedto the powder part 92, by means of the vacuum pump 20.

Alternately, the agitator rod 40 may be left in a fully down position inwhich the rigid blades 60 contact the plunger 30. The plunger 30includes an indent 108 to provide sufficient space to enable the poppetvalve 56 to downwardly open. The handle 84 of the vacuum pump 20 can beslowly squeezed to gently draw the monomer into the bottom of the mixingchamber 24, to allow the powder part to sink into the liquid part, thusadding the powder part to the liquid part.

Once the liquid part is completely emptied from the bore 52 of theagitator rod 40, the second container 14 is detached from the connector54 and the vacuum indicator 88 is removed from the handle 84 of thevacuum pump 20 and placed on the connector 54 to seal the agitator rod40 (FIG. 2). The handle 84 is squeezed until the vacuum indicator 88indicates that the desired vacuum level is reached. The agitator rod 40can then be pushed into the mixing chamber 24 so that the flexiblepaddles 58 and the rigid blades 60 contact the mix. The agitator rod 40is turned clockwise and pressure is slowly applied to the handle 53 toimmerse the flexible paddles 58 and the rigid blades 60 into the mix. Itis preferable to perform numerous clockwise turns in combination with aslow descent of the agitator rod 40 until the rigid blades 60 reach theplunger 30. For improved mixing results and degassing, the cap 32 can betapped on a solid surface every several rotations of the agitator rod40. Upon reaching the plunger 30, the clockwise rotation of the agitatorrod 40 is continued, while the flexible paddles 58 and the rigid blades60 are preferably slowly raised within the mix until the flexiblepaddles 58 reach the upper end 28 of the mixing chamber 24. The mixingprocedure is continued by slowly lowering the flexible paddles 58 andrigid blades 60 back into the mixing chamber 24 with clockwise rotationsand then raising the agitator 18, until the prescribed mixing time forthe reaction material is reached.

During mixing, the plunger 30 rises only a very small distance in themixing chamber 24 under the influence of the vacuum because the cap 32forms an airtight seal on the first container 12. As the pressuredifferential force tries to move the plunger 30 toward the upper end 28of the mixing chamber 24, the small amount of air at atmosphericpressure located between the plunger 30 and the cap 32 is quicklyreduced to a vacuum and the plunger 30 movement stops as a force balanceis achieved.

During mixing, the rigid blades 60 cut the mix and contact the wall 22of the first container 12 and scrape the powder part from the wall 22and radially inward toward the center of the mixing chamber 24. Theflexible paddles 58 simultaneously gently knead the mix and integratethe parts of the reaction material together. The combined action of therigid blades 60 and the flexible paddles 58 forms channels through themix, allowing entrapped air to escape to the vacuum. The rigid blades 60and the flexible paddles 58 are sized and shaped so that they can reachsubstantially all of the open space in the mixing chamber 24 forenhanced agitation of the mix.

The slow, alternating in-and-out axial and rotational movement of theagitator 18 within the evacuated mixing chamber 24 can quickly produce auniform, de-gassed material. The progress of the mix can be visuallyinspected through the wall 22 of the first container 24. Once thereaction material is mixed for the specified amount of time, or justbefore the end of the specified mix time as gas is being evolved fromthe reaction material, the handle 84 of the vacuum pump 20 can be pumpedas needed to maintain the vacuum pressure in the mixing chamber 24within the recommended range for the mixture.

All of the reaction by-product gases and removed air are evacuatedthrough the filter 72 by the vacuum pump 20.

Once mixing is completed, the vacuum is maintained and the agitator rod40 is raised so that the flexible paddles 58 are disposed at the neck110 of the first container 12. In this position, the user firmly graspsthe first container 12 with a hand placed preferably at about thelocation of the flexible paddles 58 and the rigid blades 60 in themixing chamber 24. This firm grasp coupled with the semi-rigidconstruction of the first container 12 substantially prevents theagitator 18 from rotating. The agitator rod 40 is then rotated in thecounter-clockwise direction while grasping the connector 16 and thevacuum pump 20 with the user's other hand. The counter-clockwiserotation unscrews the agitator rod 40 from the rigid blades 60 and theflexible paddles 58. Next, the first container 12 is unscrewed from theconnector 16 by continuing the counter-clockwise rotation. Clockwiserotation during mixing maintains the gas-tight seals, whilecounter-clockwise rotation disassembles the apparatus (for right-handthread connections). With the first container 12 detached from theconnector 16, the cap 32 is then removed from the first container 12 andthe first container 12 is placed in an extruding device such as a bonecement extrusion gun (not shown). A selected nozzle (not shown) for theextrusion procedure is attached via the threads 34 to the upper end 28of the first container 12. The mix is then extruded into the surgicalsite.

Alternately, with the flexible blades 58 positioned adjacent to the neck110 and the connector 16, the cap 32 can be removed and the handle 84 ofthe vacuum pump 20 can be gently pumped to raise the plunger 30 upwardunder the action of the vacuum within the mixing chamber 24, the plunger30 collecting the mixed material from the wall 22 as it moves. When theplunger 30 is positioned against the mix, the agitator rod 40 and theconnector 16 can be unscrewed as described above, breaking the vacuumand preparing the mix for extrusion.

As the mix is extruded from the extruding device, which pushes on theplunger 30, the flexible paddles 58 collapse and fold back and downwardinto open spaces between the individual rigid blades 60. This foldingaction is the result of the shape of the flexible paddles 58 and theirangular positioning on the agitator 40 with respect to the rigid blades60, and allows substantially all of the mix to be extruded from themixing chamber 24.

Thus, the apparatus 10 and method of mixing and dispensing multi-partreaction materials according to the present invention provides a numberof important advantages. The apparatus 10 can rapidly introduce one partinto another part in accordance with mixing schedules for the reactionmaterials. The mixing action avoids cavitation in the material mix andalso reduces the entrapment of air. The apparatus 10 can efficientlyagitate substantially the entire mixing chamber 24 at slow agitationspeeds. The construction of the flexible paddles 58 and the rigid blades60 exposes a large amount of surface area of the mix to vacuum, enablingtrapped air and reaction gases to escape from even viscous mixes. Theflexible paddles 58 and the rigid blades 60 move in unison to both cutthe mix and scrape the wall 22 to well integrate the parts of the mix.In addition, the small mixing chamber 24 enables a vacuum to be quicklyestablished and easily maintained.

The present invention can be provided as a kit. For example, when usedto mix bone cement, the kit can include the powder part of the bonecement pre-packaged in the mixing chamber 24, and the liquid partpre-packaged in the second container 14, with the entire apparatus 10,including the attached vacuum pump 20 sterilized and ready for use.

The present invention has been described in considerable detail withreference to certain preferred embodiments thereof, however, otherembodiments are possible. Therefore, the spirit and scope of theappended claims should not be limited to the description of thepreferred embodiments contained herein.

What is claimed is:
 1. An apparatus for mixing reaction materials undera vacuum, comprising:a) a container including a wall, an open firstportion, an open second portion, and a mixing chamber sized to contain areaction material during mixing; b) a closure at the second portion; c)an agitator for mixing the reaction material to form a mix, the agitatorincluding:i) a plurality of rigid blades in the mixing chamber, therigid blades being sufficiently rigid so as to be substantiallynon-deflected during mixing of the reaction material; and ii) aplurality of flexible paddles in the mixing chamber, the flexiblepaddles being sufficiently flexible so as to be deflected during mixingof the reaction material;wherein the rigid blades and the flexiblepaddles contact the wall of the container; and d) a channel in flowcommunication with the mixing chamber, gas being drawn from the mixingchamber through the channel to form a vacuum therein.
 2. The apparatusof claim 1, further comprising an indicator to indicate the vacuumpressure in the mixing chamber.
 3. An apparatus for mixing reactionmaterials under a vacuum, comprising:a) a first container including awall, an open first portion, an open second portion and a mixing chambersized to contain a reaction material during mixing; b) a closure at thesecond portion; c) an agitator for mixing the reaction material to forma mix, the agitator including:i) an agitator rod disposed in the mixingchamber and extending outwardly of the first container through the firstportion; ii) at least one rigid blade in the mixing chamber, the rigidblade being sufficiently rigid so as to be substantially non-deflectedduring mixing of the reaction material; and iii) at least one flexiblepaddle in the mixing chamber, the flexible paddle being sufficientlyflexible so as to be deflected during mixing of the reactionmaterial;wherein at least one of the rigid blades and at least one ofthe flexible paddles contact the wall of the container; and d) a channelformed in the agitator rod and in flow communication with the mixingchamber, gas being drawn from the mixing chamber through the channel toform a vacuum therein.
 4. The apparatus of claim 3, further comprising aconnector and a vacuum pump attached to the second portion of the firstcontainer, the connector including a first passage through which theagitator rod extends, and a second passage through which gas is drawnfrom the mixing chamber by the vacuum pump to form the vacuum.
 5. Anapparatus for mixing reaction materials under a vacuum, comprising:a) acontainer including a wall, an open first portion, an open secondportion and a mixing chamber sized to contain a reaction material duringmixing; b) a closure at the second portion; c) an agitator for mixingthe reaction material to form a mix, the agitator including:i) at leastone rigid blade in the mixing chamber, the rigid blade beingsufficiently rigid so as to be substantially non-deflected during mixingof the reaction material; and ii) at least one flexible paddle in themixing chamber, the flexible paddle being sufficiently flexible so as tobe deflected during mixing of the container;wherein at least one of therigid blades and the flexible paddles contact the wall of the mixingchamber; d) a channel in flow communication with the mixing chamber, gasbeing drawn from the mixing chamber through the channel to form a vacuumtherein; and e) a plunger sized to be inserted into the mixing chamber,the plunger being axially movable in the mixing chamber, to dispense themix from the first container.
 6. An apparatus for mixing reactionmaterials under a vacuum, comprising:a) a first container including awall, an open first portion, an open second portion and a mixing chambersized to contain a reaction material during mixing; b) a closure at thesecond portion; c) an agitator for mixing the reaction material to forma mix, the agitator including:i) at least one rigid blade in the mixingchamber, the rigid blade being sufficiently rigid so as to besubstantially non-deflected during mixing of the reaction material; andii) at least one flexible paddle in the mixing chamber, the flexiblepaddle being sufficiently flexible so as to be deflected during mixingof the reaction material;wherein at least one of the rigid blades and atleast one of the flexible paddles contact the wall of the firstcontainer; d) a channel in flow communication with the mixing chamber,gas being drawn from the mixing chamber through the channel to form avacuum therein; and e) a second container removably attached to thefirst container for containing a portion of the reaction material priorto introduction of the portion into the mixing chamber.
 7. An apparatusfor mixing reaction materials under a vacuum, comprising:a) a containerincluding a wall, an open first end, an open second end, and a mixingchamber sized to contain a reaction material during mixing; b) a closureremovably attached at the second end of the first container; c) anagitator for mixing the reaction material in the mixing chamber to forma mix, the agitator including:i) an agitator rod disposed in the mixingchamber and extending outwardly of the first container through the firstend; ii) a plurality of rigid blades extending radially outward from theagitator rod and contacting the wall of the container, the rigid bladesbeing sufficiently rigid so as to be substantially non-deflected duringmixing of the reaction iii) a plurality of flexible paddles extendingradially outward from the agitator rod and contacting the wall of thecontainer, the flexible paddles being sufficiently flexible so as to bedeflected during mixing of the reaction material,wherein the rigidblades and the flexible paddles being rotatable in the mixing chamber toform the mix; d) a bore through which a part of the reaction material isintroduced into the mixing chamber; and e) a channel through which gasis drawn from the mixing chamber to form a vacuum therein.
 8. Theapparatus of claim 7, comprising a second container, a breakablecontainer enclosing the part of the reaction material, and means forbreaking the breakable container to release the part therefrom such thatthe part is drawn into the bore and introduced into the mixing chamberunder the action of the vacuum.
 9. The apparatus of claim 7, furthercomprising a connector and a vacuum pump, the connector being attachedto the second end of the first container, the connector including afirst passage through which the agitator rod movably extends, and asecond passage through which gas is drawn from the mixing chamber by thevacuum pump.
 10. The apparatus of claim 7, further comprising a plungersized to be inserted into the mixing chamber, the plunger being axiallymovable in the mixing chamber to dispense the mix from the firstcontainer.
 11. The apparatus of claim 7, further comprising an indicatorto indicate the vacuum pressure in the mixing chamber.
 12. The apparatusof claim 7, comprising at least two flexible paddles and at least fourrigid blades.
 13. A kit comprising:a) a first container including awall, an open first end, an open second end and a mixing chamber; b) aclosure at the second end; c) a second container removably connectableto the first container; d) an agitator for mixing a reaction material inthe mixing chamber to form a mix, the agitator including:i) an agitatorrod disposed in the mixing chamber and extending outwardly of the firstcontainer through the first end; ii) at least one rigid blade on theagitator rod, the rigid blade being disposed in the mixing chamber andcontacting the wall of the first container, the rigid blade beingsufficiently rigid so as to be substantially non-deflected during mixingof the reaction material; and iii) at least one flexible paddle on theagitator rod, the flexible paddle being disposed in the mixing chamberand contacting the wall of the first container, the flexible paddlebeing sufficiently flexible so as to be deflected during mixing of thereaction material; e) a bore in flow communication with the mixingchamber and the second container; and f) a vacuum pump removablyconnected to the first container for drawing gas from the mixing chamberto form a vacuum therein.
 14. The kit of claim 13, comprising aplurality of rigid blades and a plurality of flexible paddles, eachcontacting the wall of the mixing chamber.
 15. The kit of claim 13,further comprising a first part of a reaction material and a second partof the reaction material.
 16. The kit of claim 15, wherein the firstpart comprises a liquid part of a bone cement mix, and the second partcomprises a powder part of the bone cement mix.
 17. The kit of claim 13,further comprising a connector removably attached to the second end ofthe first container, the connector including a first passage throughwhich the agitator rod extends, and a second passage through which gasis drawn from the mixing chamber by the vacuum pump.
 18. The kit ofclaim 13, further comprising a plunger sized to be inserted into themixing chamber, the plunger being axially movable in the mixing chamberto dispense the mix from the first container.
 19. The kit of claim 13,further comprising an indicator to indicate the vacuum pressure in themixing chamber.
 20. A method comprising:a) providing an apparatus asdefined in claim 1, 2, 5, or 6: b) forming a vacuum in the mixingchamber; c) introducing a reaction material into the mixing chamber; andd) moving the rigid blades and flexible paddles in the mixing chamber toform a mix of the reaction material under the vacuum.
 21. The method ofclaim 20, wherein the reaction material comprises a bone cement mix. 22.The method of claim 20, further comprising dispensing the mix from themixing chamber.
 23. The method of claim 20, wherein introducingcomprises drawing a part of the reaction material into the mixingchamber under the vacuum.